Replaceable filter cartridge with support element and liquid filter with such a filter cartridge

ABSTRACT

A replaceable filter cartridge assembly for a liquid filter and a liquid filter in which such a filter cartridge is installed. The filter cartridge  10  is provided with a support element  15,  and a seat  20  for a sealing membrane  19  is provided on the support element  15.  The sealing membrane seals the inlet  22  of the housing via a sealing edge  21  that acts as a return flow barrier over the inlet. The sealing membrane  19  also has a radial sealing surface  23  to provide a seal between the support element  15  and the outlet port  24  of the filter. This permits the filter cartridge to be manufactured in a particularly cost-effective manner and assures simple mounting within the housing. Since only the filter cartridge, which can be pushed onto the support element  15,  needs to be exchanged, very little material has to be disposed of when the filter is replaced, which further increases the cost-effectiveness of the filter in use.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a exchangeable filter cartridge for aliquid filter with an annularly constructed filter medium arranged on asupport element. The invention further relates to a liquid filter inwhich such a filter cartridge is installed.

[0002] Filter cartridges of the initially described type are known, forinstance, from U.S. Pat. No. 5,413,712. This document describes a filtercartridge comprising a support tube holding the filter medium whose endfaces are provided with end disks. This filter cartridge can be replacedby removing a cover from the filter housing. A spring in the coverpushes the installed filter cartridge axially against a centrallyarranged outlet port. A sealing membrane provides an axial seal betweenthe outlet port and the end disk of the filter cartridge. The sealingmembrane is simultaneously configured as a return flow barrier or checkvalve.

[0003] The disadvantage of the described prior art is the use of aspring to produce an axial force to act against the seal. This spring isan additional component in the filter unit and thus reduces the economicefficiency of the solution. Moreover, the axial force that can beapplied by the spring to provide a seal is limited. Increasing the axialforce by making the spring stiffer has the disadvantage of increasingthe closing forces that have to be applied to the cover, which makes itmore difficult to replace the filter element.

SUMMARY OF THE INVENTION

[0004] It is an object of the invention to provide a cost effectivefilter cartridge.

[0005] Another object of the invention is to provide a filter cartridgewhich is easily mountable in a filter.

[0006] A further object of the invention is to provide a filter unitincluding a cost effective, easily mountable filter cartridge.

[0007] These and other objects are achieved in accordance with thepresent invention by providing an exchangeable filter cartridge assemblyfor a liquid filter comprising an annular filter medium with sealed endfaces; a support element mounted interiorly of the annular filter mediumfor supporting the filter medium, the support element having a seat inan end area for a sealing membrane which serves as a return flowbarrier, the sealing membrane having a sealing edge for support insidethe liquid filter and for sealing a filter inlet, and an additionalsealing surface to provide a radial seal between the support element anda filter housing.

[0008] In accordance with a further aspect of the invention, the objectsare achieved by providing a liquid filter comprising an openable housingwith an inlet and an outlet, and an annular filter cartridge disposed ona central support element in the housing, an elastic sealing membraneconnected to a seat provided on one end of the support element, thesealing membrane having a sealing edge which is supported inside thehousing in such a way that it forms a return flow barrier over theinlet.

[0009] The filter cartridge according to the invention has a supportelement, which is surrounded by an annular filter medium. The supportelement may have a circular or elliptical cross section. It must haveopenings through which the liquid from the filter medium can flow intothe interior of the support element. The filter medium is mounted on thesupport element in such a way that the support element prevents it frombeing deformed or collapsing. The filter medium is preferably made of apleated or star-folded filter paper. Alternatively, rolls of a nonwovenmaterial or multi-layered filter media of any shape may be used, all ofwhich have in common that they annularly surround the support element.

[0010] The invention is characterized by a seat that is formed in thesupport element to receive a sealing membrane, which may integrate twofunctions. On the one hand the sealing membrane has a sealing edge,which is supported inside the housing in such a way that the inlet issealed. When there is no flow through the filter, this creates a returnflow barrier or check valve for liquid residues that may remain in thehousing, for instance, when the filter is removed. When liquid flowsinto the inlet of the filter, the sealing edge of the sealing membraneis lifted, so that the liquid can flow into the unfiltered side of thehousing volume of the filter.

[0011] The second function of the sealing membrane is to provide adirect radial seal between the support element and any housing part.This makes it possible, for instance, to tightly separate the unfilteredside from the filtered side. It is particularly advantageous that thesupport element may be sealed with respect to an outlet port thatconnects the interior of the support element with the outlet. Theinterior of the filter simultaneously forms the filtered side of thefilter. This results in a particularly compact embodiment of the liquidfilter of the invention.

[0012] The configuration of the seat on the support element facilitatesmounting of the filter cartridge during initial installation or in anysubsequent filter replacement. The filter cartridge and the sealingmembrane can be preassembled and then inserted into the housing. Thefilter cartridge unit, as a whole, is simple to handle, which minimizespossible installation errors. At the same time, the radial seal betweencenter tube and housing assures that the filter functions reliably,since axial tolerances are not critical to the functioning of the seal.An additional spring to produce the axial pressure of the filtercartridge against the housing is not necessary and can be omitted. Thissimultaneously reduces the mounting forces required to screw on thecover and consequently simplifies the mounting process.

[0013] In accordance with a further embodiment of the invention, thesealing membrane is permanently connected to the end area of the supportelement. This may be accomplished, for instance, by producing thesupport element using a two-component molding technique. For instance,the support element can be injection-molded from plastic and the sealingmembrane from an elastomer that adheres to the plastic. Another optionis to adhesively bond the sealing membrane to the support element. Ineither case, the reliability of the seal between support element andsealing membrane is enhanced, which increases the reliability of thefilter unit.

[0014] In a further embodiment of the invention, the end area of thesupport element is provided with a safety interlock to create a form-fitconnection between sealing membrane and support element. This assuresthat the sealing membrane will remain securely on the filter cartridgewhen the cartridge is removed. This can be accomplished, in particular,in that the form-fit connection acts in the direction of the radial sealbetween support element and housing. As long as there is increasedfriction during removal between these two components as a result of thesealing effect, the form-fit connection between the sealing membrane andthe support element is simultaneously assured.

[0015] When the filter cartridge is removed, however, the sealingmembrane can be easily replaced since it is made of an elastomer, sothat it can be stretched to overcome the interlocking connection andremove the sealing membrane.

[0016] A further embodiment of the invention provides that the supportelement protrude axially beyond the filter medium. This createssufficient clearance for the sealing membrane, so that the functionalreliability of the filter is further enhanced.

[0017] In accordance with one specific embodiment of the invention, thefilter cartridge is constructed in such a way that the filter medium isreplaceably arranged on the support element. This can be achievedparticularly in that the end faces of the filter medium are providedwith end disks or foils, which simultaneously seal the end faces of thefilter medium and provide a radial seal with respect to the supportelement. The end disks may advantageously be made of nitrile butadienerubber. This is an elastomeric mixture that remains sufficientlyresilient after a curing process to provide a seal with respect to thesupport element. The curing process simultaneously produces a tightconnection with respect to the end faces of the filter medium.

[0018] The described embodiment of the filter cartridge has theadvantage that a minimum amount of material has to be discarded when thefilter medium is replaced. Both the support tube and the sealingmembrane can be reused. The filter medium and the end disks arecompletely free of metal, which facilitates their disposal, for instanceby incineration.

[0019] If the sealing membrane is permanently connected to the supportelement, the filter medium on the support element can be replaced viathe opposite end. The support element is inserted into the new filtermedium so that a new seal is produced between the end disks and thesupport element.

[0020] The support element is advantageously made in one piece. This ispreferably accomplished by plastic injection molding and furtheroptimizes filter cartridge production with respect to costs.

[0021] A particularly advantageous embodiment of the liquid filter unitis obtained if the housing has a substantially cylindrical shape and theinlet and outlet are accommodated in the base plate of the housing. Thebase plate furthermore has a threaded socket to attach the liquid filterat the installation site. Thus the configuration essentially correspondsto that of conventional disposable filters, so that the housing of theexchangeable filter can be installed instead of a throwaway filter.

[0022] When the filter is due to be replaced, the liquid filter as awhole is unscrewed from the installation site. The sealing membraneprevents any liquid residues from flowing out of the filter housing. Thefilter housing is then opened to its optimal position so that theresidual oil remains in the housing while the filter cartridge is beingreplaced. After the housing is mounted, the liquid filter can beremounted at the installation site.

[0023] These and other features of preferred embodiments of theinvention, in addition to being set forth in the claims, are alsodisclosed in the specification and/or in the drawings, and theindividual features each may be implemented in embodiments of theinvention either individually or in the form of subcombinations of twoor more features and can be applied to other fields of use and mayconstitute advantageous, separately protectable constructions for whichprotection is also claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will be described in further detail hereinafterwith reference to illustrative preferred embodiments shown in theaccompanying drawings in which:

[0025]FIG. 1 is a cross section through the center of a liquid filteraccording to the invention; and

[0026]FIG. 2 is an enlarged detail X according to FIG. 1 showing analternative embodiment of the sealing membrane.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] The liquid filter according to FIG. 1 comprises a filtercartridge 10 disposed inside a housing 11 comprising a base plate 12 anda screw-on cover 13, which is screwed together with the base plate withan interposed O-ring 14 to form a seal. The filter assembly comprises asupport element 15 onto which is slipped a star-folded filter paper thatis provided with end disks 16 in such a way that a radial seal isobtained between the support element 15 and the end disks 16. Further,in an end area 18 of the support element, a sealing membrane 19 ismounted in a seat 20. The sealing membrane has a sealing edge 21 whichis supported against the base plate 12 and thus provides a seal withrespect to the inlets 22 which are also located in the base plate.Further, the sealing membrane has a sealing surface 23 to ensure aradial seal between seat 20 on support element 15 and an outlet port ornipple 24 which is accommodated in the base plate.

[0028] The support element further comprises a stop or abutment 25 forone of the end faces 26 of the filter cartridge 10. The filter cartridgeis pushed onto the support element prior to mounting the sealingmembrane 19 on the support tube 15. The entire filter cartridge/supporttube assembly is fixed by means of a snap connection 27 whoseinteracting elements are accommodated on the support element 15 and inthe screw-on cover 13. As a result, when the screw-on cover 13 isremoved, the filter cartridge 10 remains inside the cover.

[0029] When the filter is in operation, the fluid flows in the directionof the arrows through inlet 22 to an unfiltered side 28. It then flowsradially inwardly through filter paper 17 and reaches a filtered side29, which communicates with the interior 31 of the support tube 15 viaopenings 30 made in support element 15. From there, the filtered fluidleaves housing 11 through an outlet 32 located in the outlet nipple 24.

[0030] In addition, a schematically indicated bypass valve 33 isarranged in support element 15 in case of excessive pressure buildup.This bypass valve short-circuits the unfiltered side 28 to the filteredside 29 to assure a sufficient flow of liquid even if the filter paperclogs. Such an arrangement is important, for instance, when fluidfilters are used to filter the lubricating oil of an internal combustionengine, as depicted here.

[0031]FIG. 2 shows the liquid filter in its mounted state on theinstallation site, which is shown in part and may, for instance, be theengine block 34 of an internal combustion engine. A threaded socket 35is formed in outlet port 24 of base plate 12. Socket 35 is screwed ontoa mounting nipple at the installation site and serves to mount thefilter housing. Sealing rings 36 ensure a seal of the housing withrespect to the environment and between inlets 22 and outlet 32 of theliquid filter.

[0032]FIG. 2 further shows an alternative embodiment of the sealingmembrane 19. In this embodiment, the membrane 19 has an additional lip37, which engages with an interlocking recess 38 in seat 20 of thesupport element. As soon as the support element is pushed onto theoutlet port or nipple 24, lip 37 is pressed into the interlockingdepression 38. As a result, when the filter cartridge/support tubeassembly is removed, the sealing membrane 19 does not remain in thehousing but is separated together with the support element 15 from thebase plate 12 of the housing.

[0033] The foregoing description and examples have been set forth merelyto illustrate the invention and are not intended to be limiting. Sincemodifications of the disclosed embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed broadly to include all variations fallingwithin the scope of the appended claims and equivalents thereof.

What is claimed is:
 1. An exchangeable filter cartridge assembly for aliquid filter comprising an annular filter medium with sealed end faces;a support element mounted interiorly of the annular filter medium forsupporting the filter medium, said support element having a seat in anend area for a sealing membrane which serves as a return flow barrier,said sealing membrane having a sealing edge for support inside theliquid filter and for sealing a filter inlet, and an additional sealingsurface to provide a radial seal between the support element and afilter housing.
 2. A filter cartridge assembly according to claim 1,wherein said annular filter medium comprises a pleated filter paper. 3.A filter cartridge assembly according to claim 1, wherein the sealingmembrane which serves as a return flow barrier is permanently connectedto the end area of the support element.
 4. A filter cartridge assemblyaccording to claim 1, wherein the end area of the support element isprovided with an interlocking configuration to create a form-fitconnection with the sealing membrane.
 5. A filter cartridge assemblyaccording to claim 1, wherein the end area of the support elementextends axially beyond an adjacent end face of the filter medium.
 6. Afilter cartridge assembly according to claim 1, wherein the filtermedium is replaceably disposed on the support element.
 7. A filtercartridge assembly according to claim 1, wherein at least one end faceof the filter medium is connected with an end disk for forming a seal.8. A filter cartridge assembly according to claim 7, wherein said enddisk is made of nitrile-butadiene rubber.
 9. A filter cartridge assemblyaccording to claim 1, wherein the support element is constructed as onepiece.
 10. A filter cartridge assembly according to claim 1, wherein theadditional sealing surface of the sealing membrane forms a radial sealbetween the support element and an outlet port of the filter housing.11. A liquid filter comprising an openable housing with an inlet and anoutlet, and an annular filter cartridge disposed on a central supportelement in said housing, an elastic sealing membrane connected to a seatprovided on one end of said support element, said sealing membranehaving a sealing edge which is supported inside the housing in such away that it forms a return flow barrier over the inlet.
 12. A liquidfilter according to claim 11, wherein said housing comprises a baseplate and a screw-on cover, and said support element is detachablyconnected to the housing cover by a snap connection.
 13. A liquid filteraccording to claim 11, wherein the housing has a substantiallycylindrical shape, and the inlet and outlet are accommodated in a baseplate of the housing, said the base plate comprising a threaded socketfor attaching the liquid filter at an intended installation site, andwherein sealing rings are provided to seal the housing relative to theenvironment and to provide a seal between the inlet and the outlet. 14.A liquid filter according to claim 11, wherein said filter is an oilfilter for lubricating oil of an internal combustion engine.